German patent publication DE-AS 23 14 301 discloses a thermostatic valve unit having two thermally responsive valves located in a divided housing having inlet and outlet openings. The housing accommodates compression springs that bias the thermally responsive valve elements towards predetermined positions. The housing is a casting which incorporates connectors for the inlet and the outlet and the parts are assembled by means of threaded connectors. Seals are included where appropriate.
The thermally responsive valves carry valve disks for opening and closing against valve seats dependant upon temperature of the fluid flowing into the housing.
Such units are frequently employed in vehicular applications for water cooled engines. In these applications, such valve units may prevent coolant from traveling to the radiator, for example, during a cold start of the engine so that the engine coolant will rapidly heat and allow the engine to warm up promptly. The rapid warm up also permits rapid heating of a passenger compartment for the vehicle as well. After some predetermined temperature is reached, the coolant is then permitted to flow through the radiator to be cooled so as to maintain the coolant generally at the predetermined temperature which is an optimum temperature for engine operation.
To perform these functions, the valve unit is located in connection with the coolant line passing to and from the engine and to the coolant pump from the vehicular radiator as well as optionally from the heater core in the passenger compartment. The coolant lines are typically connected to fittings formed on the valve housing.
Many of these units are difficult to install and, because of the metal casting used as a housing, have an undesirably high weight which impacts on fuel economy. Further, as they are typically designed as the main thermostatic control valve for coolant flow, they frequently are too large and unwieldy for other applications where lesser flow rates are involved. Thus, German patent application DE-PS 44 16 240 discloses a valve that is reduced in size and weight through the use of a plastic housing. This disclosure is not of a valve unit having two thermally responsive valves, but rather, one with but a single thermally responsive valve. Consequently, such a valve does not have the ability to operate in an emergency in many applications as, for example, when the thermally responsive valve fails. Furthermore, the thermally responsive valve has a valve member on the valve body for opening and closing of flow openings, and consequently, is unduly complex.
Other thermally responsive valve units have been proposed but most typically require electrical control and incorporate a variety of relatively complex elements that are used to assure operations in an emergency situation. Again, simplicity is lacking.
The present invention is directed to overcoming one or more of the above problems.